The one-page report said Prince was dressed in black at the time of his death and was wearing a black cap.

The medical examiner's office said its investigation into Prince's death had now finished and it was unable to make any further comments.

A spokesman for Carver County Sheriff's Office said its investigation was continuing but was unable to give any further details about its progress.

Prince was found collapsed in a lift by staff members, more than 12 hours after he was last seen alive when he was dropped off at Paisley Park. He was pronounced dead at the scene and his body was later cremated.

The National Institute of Drug Abuse (NIDA), based in Maryland, US, says Fentanyl is a powerful synthetic opiate analgesic which is similar to but more potent than morphine.

Its website says it is typically used to treat patients with severe pain or to manage pain after surgery but is sometimes used to treat people with chronic pain who are physically tolerant to opiates.

Fentanyl is classed as a schedule II drug in the US which means the prescription drug is considered dangerous with a high potential for abuse. Use of the drug can use potentially lead to severe psychological or physical dependence.

The Purple Rain star was rushed to hospital six days before his death after he was found unconscious on a plane after it stopped in Moline, western Illinois. He was given a drug used to treat suspected overdoses.

Celebrity news website TMZ reported that he had overdosed on a painkiller called Percocet which contains the opioid oxycodone.

Prescription drugs were found at Prince's home following his death.

Prince's long-time friend and collaborator Sheila E said he had hip and knee problems that were the result of years of jumping off speakers in heels while performing on stage.